cPickle fails on large objects, throwing a SystemError exception which is cryptic. 

The issue was fixed for pickle in python 3 back in 2011 (http://bugs.python.org/issue11564), but never addressed in 2.7.  It seems to be a recurring complaint (e.g., http://bugs.python.org/issue11872), but always seems to be closed without being fixed or explained why it cannot be fixed.

Test case from 2011 still fails:

>>> import cPickle; cPickle.dumps('a' * (2 ** 31),-1)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
SystemError: error return without exception set